Python Template Strings — ELI5

You know those Mad Libs games where you have a story with blanks?

“Dear _____, thank you for the _____ gift.”

You fill in the blanks and get a complete sentence.

Python has something almost identical called Template strings.

You write a message with placeholders marked by a dollar sign: $name or ${item}. Then you tell Python what goes in each blank.

"Dear $name, thank you for the $gift."

Fill in name = "Grandma" and gift = "awesome", and you get:

“Dear Grandma, thank you for the awesome gift.”

Why not just use f-strings or .format()?

Those are powerful but a bit too powerful. They can run code inside the placeholders. If someone sneaky puts weird stuff in the blanks, bad things might happen.

Template strings are deliberately simple. They can only do one thing: replace $name with a value. No math, no function calls, no tricks.

That makes them perfect when the template comes from someone you don’t fully trust — like a user filling in their own message, or a config file from an outside source.

When to use them:

• User-supplied message templates
• Config files with variable substitution
• Any time safety matters more than fancy features

When NOT to use them:

• When you control the template yourself (f-strings are faster and more flexible)
• When you need expressions or formatting inside placeholders

One Thing to Remember

Template strings are the safe, simple way to fill in blanks — they do substitution and nothing else, which is exactly the point.